In a known motor-driven chain saw, forward and rearward handles are provided, which are connected by respective antivibration elements to the drive unit. The rearward handle comprises a handle which has an extension extending in the longitudinal direction of the chain saw. The extension has a forward end which is attached to a handle tube. The handle tube extends over the drive unit and is fixed with its other end to the handle housing. In practice, it has been determined that resonance frequencies occur under specific operating conditions and these resonance frequencies are a burden to the operator and contribute to making work with the apparatus tiring.
It is an object of the invention to provide a work apparatus wherein the damping of vibrations is improved.
The portable handheld work apparatus of the invention includes a motor-driven chain saw and defines a longitudinal axis. The portable handheld work apparatus includes: a drive unit; a handle housing defining a rearward handle; antivibration means for connecting the handle housing to the drive unit; a guide bar connected to the drive unit; the handle housing having a first end facing away from the guide bar with the first end being in the longitudinal direction of the guide bar and the handle housing having a second end facing toward the guide bar; the handle housing having an extension member extending forwardly from the rearward handle at the first end to the second end; the extension member having a free end portion; a forward handle tube passing over the drive unit transversely to the longitudinal axis; the forward handle tube having a first end attached to the free end portion and a second end attached in the region of the rearward handle; and, one of the first and second ends of the forward handle tube being fixed via an antivibration element.
The transmission of vibrations to the handle tube (the vibrations occur in the handle housing or are transmitted thereby) are reduced by decoupling the handle tube from the handle housing by a vibration element at least at one end of the handle tube. The entire system is modified with respect to vibrations so that burdensome resonances are shifted out of the normal operating range and can no longer affect the operator. In an embodiment of the invention, both ends of the handle tube are attached to the handle housing via respective antivibration elements.
Advantageously, one of the ends of the handle tube is fixed via an antivibration element to the handle housing as well as to a housing part connected to the drive unit. In this way, the transmission of vibration is reduced especially effectively. The outer boundary line of a cross section of the handle tube advantageously encloses a smaller area at an end of the handle tube facing toward the antivibration element than in a center region of the handle tube. In this way, the space, which is available for accommodating the vibration-damping element and the attachment means, is increased. The end of the handle tube can have a flat shape or can have a smaller outer diameter than a center region of the handle tube.
The antivibration element advantageously has an approximately cylindrical form and is mounted in the longitudinal direction of the handle tube. A holder, which is provided on the handle housing, encloses the antivibration element at least partially. It is especially practical to mount the rearward end of the handle tube, which is attached directly to the handle housing, within the vibration-damping element.
According to another embodiment of the invention, the antivibration element is configured as a bushing having a collar and the bushing is mounted in a cutout approximately perpendicular to the longitudinal axis of the handle tube.
The antivibration element is advantageously configured to be an approximately flat component. The antivibration element is configured in two parts for the embodiment of the vibration-damping element in the form of a bushing as well as for the flat configuration. The vibration-damping element partially covers the facing sides of the handle housing and/or of the handle tube. This embodiment makes possible an advantageous constructive configuration especially for the attachment of the forward end of the handle tube attached to the extension of the handle housing. With an approximately flat configuration of the vibration-damping element, the handle tube and the handle housing can be attached separately from each other to the antivibration element. This is especially so for the attachment of the rearward end of the handle tube.
The handle housing (especially the extension of the handle housing) is attached to a first region of the antivibration element and, at a second region of the antivibration element, a housing part, which is connected to the drive unit (especially the motor housing), is attached. The first and second regions are spaced from each other in the longitudinal direction of the handle tube.
The antivibration element advantageously is made of microcellular polyurethane. The material ensures an excellent damping without affecting the ability of the operator to manipulate the work apparatus.